Note: Descriptions are shown in the official language in which they were submitted.
International Application Number: IB2015058303
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METHOD AND APPARATUS FOR APPLYING A HEAT-ACTIVATED DOUBLE-
SIDED ADHESIVE TAPE TO A SUPPORT
Field of the invention
The present invention relates to a method and apparatus for applying a heat-
activated double-sided adhesive tape.
More in particular, the present invention relates to a method for optimizing
the
process of applying a heat-activated double-sided adhesive tape to a support,
typically a support made of elastomeric material, thermoplastic material, PVC,
silicones and so forth.
A further object of the present invention is an apparatus adapted to implement
said
method for applying double-sided adhesive tape to a support.
Description of the prior art
It is known in various industrial sectors, e.g. in the automotive sector, to
use double-
sided adhesive tapes to obtain the adhesion by gluing of parts, e.g. seals
made of
elastomeric material, thermoplastic material, PVC, silicones and so forth, to
surfaces
of various kind.
Examples of methods and apparatus according to the prior art for applying
adhesive
tapes to a support are known from US 5 886 313.
The use of seals, in particular, is increasingly more common in various
sectors. Such
seals must guarantee the hermetic sealing during closure, e.g. of the door to
which
they are applied, when referring to the automotive sector. In the assembly
processes
of such seals to the surfaces, e.g. to the metal surface of a door referring
again to
the automotive field as non-limiting example of application, the seals reach
the
assembly chain already provided with a double-sided adhesive for fixing the
seal to
the surface.
Such double-sided adhesive tape is glued in advance to the seal by means of an
application technique which includes the use of a heat source adapted, as
known,
to activate the double-sided adhesive tape.
The type of double-sided tape to which the method and apparatus according to
the
present invention relates is thus a tape comprising at least one layer of
acrylic foam,
or similar expanded material, said at least one layer of acrylic foam being
covered
by a heat-activated adhesive substance on one side and covered with a so-
called
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AMENDED SHEET
International Application Number: IB2015058303
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Article 34 Amendments
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13436PTW0_20160829_AMD page 1, la clean
liner, i.e. by a thin layer of polymeric material, e.g. polyethylene, adapted
to be
removed to allow the tape to be glued to a support, on the other side.
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Thus, more in particular, the double-sided adhesive tape treated by the method
and
apparatus according to the present invention is used, in particular, for
gluing seals
to painted vehicle parts.
The double-sided adhesive tape thus comprises a layer of heat-activated
adhesive
on one side adapted to adhere by means of heat activation onto EPDM and TPE
rubbers, while on the other side it comprises a self-adhesive layer protected
by the
liner, which once the liner is removed allows the tape itself to be quickly
glued, and
thus the seal, to the painted vehicle part.
Besides continuous applications, the market requires intermittent applications
of
double-sided adhesive tape to a support, i.e. applications in which the
support parts
provided with double-sided adhesive tape are alternated with support portions
in
which the double-sided adhesive is not positioned, this thus requiring
automatic
apparatuses for applying reactive double-sided adhesive tape provided with an
instantaneous heat source, free from transient phenomena, the temperature of
which must be always instantaneously controlled.
The known methods for applying a double-sided adhesive tape considered hereto
require the use of an apparatus provided with opposite pulleys through which
the
double-sided adhesive tape and the support on which said double-sided adhesive
tape must be applied are simultaneously passed.
The two pulleys must apply a regular, constant pressure between the two
elements,
double-sided adhesive tape and support, and for the coupling to occur
correctly both
elements must be aligned and guided in a linear, constant manner during the
step
of insertion into the pulleys.
The adhesion of the double-sided adhesive tape may be performed cold, with the
use of primer and glue, or in the case of the heat-activated double-sided
adhesive
tapes considered hereto, by means of heat activation of the glues already
present
in the double-sided adhesive tape. Such glues are activated at a predetermined
temperature, which is thus a fundamental parameter of the adhesion process.
In the adhesion process of a heat-activated adhesive of the type considered
here to
a support, it is thus fundamental to heat the union zone between the adhesive
and
the support to the activation temperature of the adhesive, and is fundamental
for the
correct outcome of the process that such a temperature is maintained constant,
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uniform throughout the adhesion zone and that there are no transients during
the
process, for example related to the reaching of the activation temperature
during the
step of starting up the process.
Not last, it is also very important that the heating of the heat-activated
adhesive layer
is performed on a level which is necessary and sufficient to obtain the
activation of
the adhesive itself but at the same time is such not to cause an excessive
heating
of the acrylic foam layer, which would cause as negative effect the heating
and the
consequent damaging of the adhesive placed on the opposite side of the acrylic
foam with respect to the heat-activated double-sided adhesive tape.
Damaging the adhesive under the liner would compromise the possibility of
effectively gluing the double-sided adhesive tape and the support, e.g. the
seal, on
which the double-sided adhesive tape is glued by means of the method and
apparatus object of the present invention, and may also damage the liner
itself which
appears wrinkled and raised in multiple points from the acrylic foam layer as
a
consequence of the damage of the adhesive on liner side.
Currently, the methods and apparatuses of known type use heating elements,
such
as for example a hot air emitters (blowers) and heat resistors which take the
heat-
activated adhesive to activation temperature when correctly oriented.
As mentioned, the process also requires a heating of the support, e.g.
consisting of
the seal, which is hit by the hot air and is thus also considerably heated, in
addition
to the adhesive tape.
The heating of the support is another fundamental aspect for the good result
of the
adhesion process of the adhesive, and for this purpose it is known to provide
infrared
lights with strong heating power which increase the temperature of the support
before the application of the double-sided adhesive tape.
The known methods for applying a double-sided adhesive tape have many
drawbacks.
Firstly, the use of heating elements such as hot air emitters and heating
resistors
also causes a heating of parts of the apparatus surrounding in the union point
between double-sided adhesive tape and support, thus compromising the quality
of
the end result because of the impossibility of concentrating the action of the
source
of heat in one point. Indeed, an uncontrolled increase of the temperature of
the
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pulleys which transport the double-sided adhesive tape may, for example, cause
damage to the liner, i.e. to the very thin part of the tape which is applied
onto the
surface of the double-sided adhesive tape to cover the zone not in contact
with the
support and which is removed when the support must be glued to the end
product,
for example to the door of a vehicle.
Another drawback which afflicts the methods of known type is the risk of early
activation of the heat-activation process of the adhesive when the double-
sided
adhesive tape and the support are not yet in the correct reciprocal coupling
position
inside the pulleys.
A further drawback which afflicts the methods of known type consists in the
risk that
the high increase of temperature of the support could cause a deformation of
the
support by heat expansion. Since the support has a different thermal
coefficient from
that of the double-sided adhesive tape to which it must be coupled, the
thermal
deformation of the support may cause mechanical stresses once the double-sided
adhesive tape has been applied and the elements have been cooled, which may
bend the seal itself or wrinkle the liner, and thus ultimately the double-
sided
adhesive tape.
In order to reduce the effects of overheating, it is necessary with the
methods and
apparatuses of the known type, to cool all the parts concerned by the
undesired
heating by means of liquid, i.e. with jets of water, with considerable
increase of costs
and dimensions of the apparatus which performs the adhesion.
Again, the apparatuses of known type which use heating means as described
require a relatively long time before the process of applying the double-sided
adhesive tape stabilizes, because there is a transient step for the activation
temperature of the double-sided adhesive tape to be reached, because the
reaching
of the desired temperature by the heating means is not instantaneous. This
transient
step inevitably creates waste material whenever the adhesion process is
started and
before it has warmed up.
Some known solutions of the prior art use laser apparatuses for applying tapes
or
covering layers of composite materials to a substrate.
An example of method and apparatus of known type is shown in US 6,451,152 B1,
in which a tape of composite material is applied to an article made of
composite
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material by heating by means of an array of laser diodes which may be
activated
independently from one another so as to control the emitted power.
The patent teaches the use of an array comprising a plurality of laser diodes
in order
to allow a uniform energy distribution on a support and on a tape made of
composite
material in order to optimize the energy distribution as the application
conditions of
the tape vary, in particular to change the heating as a function of the
curvatures of
the support surface on which the tape must be applied.
Indeed, the patent states that if the heating of the tape is optimized for a
given speed
of the head which deposits the tape on the support when the surface of the
latter is
flat, the energy itself will be insufficient to heat the tape in the convex
regions, while
it will be excessive in the concave regions.
Prior document US '152 is thus not directed to the application of a heat-
activated
double-sided adhesive tape of the type considered here to a support of rubbery
material, but is instead directed to the application of a composite material
tape to a
support also made of the same material.
Furthermore, the prior document does not teach to optimize the productivity of
the
tape deposition process in terms of application speed, but instead examines
another
technical problem, consisting in the need to vary the energy density which
hits the
tape.
Patents EP 1 334 819 Al and US 2012/0285604 Al are also known in the prior
art.
EP 1 334 819 Al again relates to a method of layered application of composite
materials and also in this case teaches to use a laser diode array. Also in
this case,
the control of the zones of the composite fibers to be treated occurs by means
of a
controller complex which determines the controlled switching on and off of the
numerous diodes of the array. The prior patent requires each diode of the
array to
be connected to an independent power source so as to control the diodes
independently from one another.
EP 819 solves the technical problem of optimizing the energy density
distributed as
a function, for example, of the dimensions of the fibers to be treated, which
may be
different, of the type of material of the fibers, which also in this case may
be different,
and so on.
For this reason, an array comprising a plurality of diodes and laser power
sources
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allows the heating level to be optimized also according to the geometry of the
substrate, which may have a non-flat surface and different curvature radii.
Ultimately, prior document US 2012/0285604 Al describes a method and a device
for covering artifacts made of wood, plastic or other similar materials, in
which the
use of at least two energy sources is described very generically. Such energy
sources may consist of laser, infrared, ultrasound, magnetic field, microwave,
plasma, gas emitters, and so on.
Thus, the patent does not teach to optimize the gluing production process of a
heat-
activated adhesive of the type considered here nor does it relate to the
productivity
of an apparatus of the type which is the object of the present invention.
Summary of the invention
It is thus the main task of the present invention to provide a method and
apparatus
for applying a heat-activated double-sided adhesive tape of the above-
described
type, i.e. comprising a layer of heat-activated adhesive to a support which
allows
the drawbacks afflicting the methods and apparatus of known type to be solved.
Within this task, it is the object of the present invention to provide a
method which
allows the step of heating the heating means to be completely eliminated, thus
considerably reducing or even completely eliminating waste, while completely
eliminating the problems of deformation of the support caused by the heating
thereof.
It is a further object of the present invention to provide a method for
applying a heat-
activated double-sided adhesive tape to a support which allows to have an
instantaneous heating, which can be modulated and localized in the adhesion
zone
between double-sided adhesive tape and support.
Not last, it is the object of the present invention to provide a method in
which only
the portions of the support concerned by the application of the adhesive, and
not
the entire support, are heated.
It is also an object of the present invention to provide an apparatus for
applying a
heat-activated double-sided adhesive tape to a support which allows the method
object of the present invention to be implemented and which is simpler to be
manufactured, and thus more cost-effective.
In particular, it is the object of the present invention to provide an
apparatus for
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applying a heat-activated double-sided adhesive tape to a support which does
not
require cooling means and which offers a high modularity and an accurate
control
of the caused heating.
It is yet another object of the invention to optimize the deposition process
of a heat-
activated double-sided adhesive tape of the type considered here, thus
improving
the productivity of the machine suited to implement said method, while
obtaining an
improvement of the final result in quality terms and an improvement of the
productivity of the apparatus in terms of reduction of the process times
necessary
for the application of the support tape.
It is yet another object of the present invention to provide a method and
apparatus
adapted to implement said method, said apparatus being obtained in a simple
manner by changing the apparatuses of known type which use hot air for heating
the support, thus allowing the retrofitting of such apparatuses of known type
in a
simple, cost-effective manner.
This task and these and other objects are achieved by a method for applying a
heat-
activated double-sided adhesive tape and by an apparatus adapted to implement
said method according to the appended independent claims.
Further features of the method and apparatus are mentioned in the dependent
claims.
Brief description of the drawings
Further objects and advantages of the present invention will become apparent
from
the detailed description of a preferred embodiment of the present invention
which is
shown by way of non-limiting example in the accompanying drawings:
Figure 1 diagrammatically shows a preferred embodiment of the apparatus for
applying a heat-activated double-sided adhesive tape according to the present
invention;
Figure 2 shows a detail of Figure 1;
Figure 3 shows the Gaussian distribution of the energy emitted by the laser
sources;
Figure 4 diagrammatically shows the application of laser light to a heat-
activated
double-sided adhesive tape by means of the apparatus in Figures 1 and 2;
Figure 5 shows the Gaussian distribution of the laser light generated by the
apparatus according to the present invention;
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Figure 6 diagrammatically shows the reciprocal positioning of the laser light
sources
of the apparatus according to the present invention;
Figure 7 shows an overview of a preferred embodiment of the apparatus applying
a
heat-activated double-sided adhesive tape according to the present invention.
Description of the preferred embodiment
According to a preferred embodiment described here by way of non-limiting
example
of the method for applying heat-activated double-sided adhesive tape according
to
the present invention, a laser light is used for causing the heating of the
heat-
activated adhesive substance present on the double-sided adhesive tape to
obtain
the adhesion of the double-sided adhesive tape to the surface of a support.
With reference to the accompanying figures, the method according to the
present
invention allows the heat-activated double-sided adhesive tape 10 to be fixed
to a
support 20 by using two laser light emitters 30, each comprising an optical
collimator
31 capable of projecting a cylindrical light beam 33. The laser light emitters
30 may
be each connected by means of an optical fiber 32 to a single laser light
generator,
not shown in the accompanying figures.
The method according to the present invention comprises the following steps:
- preparing a support 20 on which said heat-activated double-sided tape 10
is
adhered, and a heat-activated double-sided tape 10;
- hitting at least one portion of said double-sided tape 10 with laser light
from
at least two different laser light emitters 30, in order to obtain at least
one
activated zone of double-sided tape 10;
- bringing into mutual contact said at least one zone of activated double-
sided
tape 10 with said support 20 in a contact zone.
The method according to the present invention may further include also hitting
at
least one part of the support with said laser light from at least two emitters
30.
Said method further comprises the step of applying a pressure force between
said
support 20 and said double-sided adhesive tape 10 in the activated condition
at said
contact zone, as well as at least one step of calibrating the convergence and
partial
overlapping of the light beams 33 generated by the laser light emitters 30.
In order to allow the implementation of the method of the present invention,
the
apparatus also object of the present invention according to a preferred
embodiment
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advantageously comprises a first wheel 40, which feeds the double-sided
adhesive
tape 10 preferably wound on a support coil, not shown in the drawings, and a
second
wheel 50 opposite to the first wheel. Said first 40 and second 50 wheels turn
with
mutually opposite sense of rotation, and their reciprocal position can be
adjusted
towards/away so that a space is defined for inserting support 20 at their
tangent
point, so that said support 20 inserted between the two wheels 40, 50 is moved
forward by their rotation.
The two opposite and adjustable wheels allow the application of a pressure
between
said double-sided adhesive tape 10 and said support 20, thus optimizing the
adhesion process.
At the same time, the first wheel 40 feeds the double-sided adhesive tape 10
which
is partially wound on it as shown in Figure 1.
The double-sided adhesive tape 10 wound on the supporting coil is
advantageously
unwound by means of a mechanical system, not shown in the figures.
The double-sided adhesive tape 10 is thus guided by means of appropriate
guiding
means to the first wheel 40 which feeds the double-sided adhesive tapel 0 to
the
contact zone with the support 50.
Advantageously, the double-sided adhesive tape 10 is guided by means of an
adjustable slide, either manually or electrically by means of a servo motor,
in order
to be positioned correctly in the contact zone.
Said first wheel 40 may be made of metal or plastic material or other
materials and
may have a smooth or lined contact surface with the tape, according to needs,
and
may be provided with a shock absorber system which, by means of pneumatic or
electric or spring means ensures that the double-sided adhesive tape 10 is
pressed
against support 20 again with the same previously set force.
In order to distribute the double-sided adhesive tape on the seal, either the
support
can be fed through a second motorized wheel 50 opposite to the first wheel 40
which
supports the double-sided adhesive tape 10 or the support 20 can be kept still
and
the first wheel 40 can be moved thus making the axis of said first wheel 20
axially
movable.
In the first case, corresponding to the preferred configuration shown in the
accompanying figures, the second wheel 50 will be motorized independently from
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the first wheel 40 in order to avoid surface stresses which are dangerous for
the
result of the application.
The second wheel 50 may also be made of metal or plastic material and must be
shaped each time according to the shape of the support section so as to
operate
also as guide for the support itself.
In the second case, corresponding to an alternative configuration of the
apparatus,
not shown on the accompanying drawings, support 20 will be appropriately
contained within a static guide according to the section of the support 20
itself.
The apparatus according to the present invention further comprises at least
two
laser light emitters 30, each comprising an optical collimator 31 capable of
projecting
a cylindrical light beam 33 in direction of the contact zone between the
double-sided
adhesive tape 10 and the support 20. The laser light emitters 30 may be each
connected by means of an optical fiber 32 to a single laser light generator or
multiple
laser light generators may be provided.
Said laser light emitters 30 being capable of generating a light having
wavelength
comprises between 780 and 1100 nanometers, preferably about 800 nanometers,
even more preferably 808 nanometers.
This range of wavelengths is such that the light is absorbed by the plastic
objects
having a dark color, such as typically the double-sided adhesive tape 10 and
the
support 20, thus accumulating thermal energy.
The laser light generated by a laser diode is preferably transported by means
of an
optical fiber 32, e.g. preferably but not necessarily a 600 pm fiber, to the
optical
collimator 31, which is oriented towards the contact between the contact point
with
the double-sided adhesive tape 10 and the support 20, as shown in figures 1,
2, 4
and 5.
The particularity of the optical collimator used is that the light beam
exiting therefrom
assumes a cylindrical shape. The laser light concentrated in a cylindrical
shape
beam preferably of about 1 centimeter causes the heating of the hit surface by
distributing the energy according to a Gaussian curve shown in figure 3,
preferably
with a super Gaussian distribution.
The apparatus according to the present invention includes using at least two
non-
confocal laser light sources 30, arranged side-by-side so as to project two
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light beams which partially overlap, as shown in figures 4, 5 and 6, at the
contact
zone of tape 10 with support 20.
Being the energy distribution of the Gaussian type, the energy in the center
of the
cylinder is higher than the outside.
The surface of the double-sided adhesive tape 10 to be activated may be up to
about
20 mm wide, and so at least two cylindrical laser light beams side-by-side and
partially overlapped must be used to maintain the energy constant and uniform
on
the entire double-sided adhesive tape surface to be activated.
By using for example two light source sources 30, each comprising an optical
collimator for obtaining a laser source cylinder of diameter of about 1 cm
each, and
partially overlapping them, it will be possible to distribute a uniform amount
of energy
on the entire surface of the double-sided adhesive tape to be activated, thus
obtaining a uniform result in terms of activation of the double-sided adhesive
tape
itself.
By manually adjusting the two collimators 31, or better still by positioning
an
electrical actuator so as to control the reciprocal position thereof
accurately, the
convergence of the cylindrical light beams 33 can be adjusted to optimize the
distribution of energy, and thus of heat, in the contact zone between double-
sided
adhesive tape 10 and support 20, thus obtaining the desired activation of the
glues
on the double-sided adhesive tape and on the support, if it is consists of a
rubber
seal, to burn the surface oils of the rubber.
To provide some parameters, the two laser light sources could have a total
power
of about 400 watt. With such a power, a heat-activated tape of the type
considered
here having a width of about 8 mm may be hit over a length of about 15 mm with
an
energy density sufficient to obtain the complete, effective gluing to the
rubber
support and allowing a feed speed of the tape of 20 meters/minute.
According to a preferred embodiment of the present invention, the method and
apparatus according to the present invention requires the two collimators 31
to be
adjustable in space.
More preferably, besides being horizontally adjustable as described above to
optimize the distribution of energy, and thus of heat, on the entire width of
the tape
as the width of the tape varies, such collimators 31 may be adjustable also
vertically
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independently from each another, e.g. by requiring collimator 31 to be hinged
to its
support by means of a hinge.
Therefore, with reference to the diagrammatic views in Figures 5 and 6, for
example,
not only the collimators 31 may be horizontally adjustable so that the light
beams 33
at least partially converge on tape 10, while arranging themselves side-by-
side
along a transversal axis A with respect to tape 10, but can be arranged to
overlap
each other along the longitudinal axis of tape 10.
With reference to Figure 1, for example, horizontal direction means the
direction
identified by the plane on which support 20 lies, and vertical direction means
a
direction vertical thereto. Similarly, with reference to Figure 5, the
transversal axis
A lies on a horizontal plane.
As mentioned, the possibility of horizontal movement, along a transversal axis
A, of
the collimators 31, and thus of the light beams 33 produced thereby, allows
the
energy density to be optimized as a function of the tape width, thus making
the
apparatus suited to implement the method and versatile in order to heat
supports
and tapes 10 having different widths.
When the width of the tape increases, the speed of the machine, and thus its
productivity, decreases for because a power density suited for activating the
heat-
activated adhesive must be supplied.
20 When the width of the tape is considerable, the two light beams 33
produced by the
collimators 31 must be arranged side-by-side possibly minimally overlapped,
and
thus there will be zones of the tape concerned by a lower energy density,
being the
distribution of energy of each light beam of the Gaussian type as mentioned.
Since the power is the product of the energy by unit of time, it results that
if the
energy density is lower, in order to obtain the power density needed to
activate the
heat-activated adhesive, it will be necessary to expose the tape to the light
energy
of the beams 33 for a longer period of time, and this is obtained by slowing
down
the feed speed of the tape.
Conversely, when the tape width is small, it is possible that one only light
beam 33
produced by a single collimator 31 supplies the energy density sufficient for
the
activation of the adhesive to the tape, and thus in this case instead of
activating a
single collimator, with the suggested solution the second collimator 31 can be
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moved vertically so that the two light beams 33 are aligned vertically on the
tape
along the transversal axis B.
Thereby, a huge advantage can be obtained in terms of possible increase of the
feed speed of the tape, with the speed of the machine even exceeding 20-25
meters
a minute, to reach over 30 meters a minute.
The advantage achieved by aligning the two light beams 33 along the
longitudinal
axis B, thus along the longitudinal axis of tape 10, is indeed not only a
consequence
of a greater heated portion of tape, but also a consequence of the further
reduction
of the step of hysteresis which leads to the activation of the heat-activated
adhesive:
by overlapping the two light beams 33, the adhesive can be preheated with the
light
beam which hits the tape first with respect to the feed direction thereof, the
beam
which hits the tape first with respect to the feed direction thereof indicated
by the
arrow in Figure 5, pre-heats the heat-activated adhesive, which is further
heated by
the second beam thus activating the adhesive nearly instantaneously.
This evidently allows a considerable increase of the process speed with a much
higher machine productivity than any process and any machine of known type in
the
prior art.
According to a preferred embodiment of the present invention, said collimators
31
may be further provided with dedicated optics which allows the light beam 33
to be
focused. Thereby, the beam itself can be converged or diverged by changing the
amplitude of the zone of the tape hit by the light beam and the energy
concentration.
The presence of dedicated optics on the collimators 31 thus allows the energy
density on the tape to be varied further.
Preferably, the method according to the present invention requires addressing
the
light source emitted by the sources 30 exclusively onto tape 10 and not onto
the
support. It has indeed been experimentally noted that in all cases support 20
indirectly receives an amount of energy sufficient for effectively completing
the
gluing process.
In order to control the adhesion process instant-by-instant and to monitor the
correct
activation of the adhesive and thus guarantee the achieved union between
double-
sided adhesive tape and support, the apparatus according to the present
invention
may advantageously comprise a temperature gauge, i.e. infrared, typically a
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pyrometer, by means of which the temperature reached by the double-sided
adhesive tape and by the support at the contact point can be instantaneously
monitored.
Thereby, visual and/or auditory alarm means can be associated if the
temperature
detected by the pyrometer during the process is out of the preset threshold
values.
Again by means of the temperature gauge, operatively connected to a control
unit,
the power of the laser light sources 30 can be automatically adjusted by means
of
the control unit so that the adhesion temperature is automatically adjusted
within the
correct threshold.
The central control unit processes the process parameters entered either
manually
by the operator, such as for example the nature of the materials of the double-
sided
adhesive tape and of the support, the width of the heat-activated adhesive
tape
and/or detected by the sensors present aboard the apparatus, such as, for
example,
the aforementioned temperature gauge, and a metric wheel (encoder) 60 which,
by
feeling the surface of support 20, checks the actual forward movement of the
support itself, and compares them with preset threshold values stored in a
storage
module.
By means of comparison and adjustment module, said control unit compares the
input process parameters with the reference parameter values stored in the
memory
module and then acts on the operating parameters of the apparatus, such as,
for
example, the position and power of the sources 30 and the feed speed of the
support
and of the double-sided adhesive tape.
Therefore, the central control unit may advantageously allow the position of
the
sources 30 to be changed automatically with respect to the contact zone
between
the heat-activated tape 10 and the support 20 during the process, by entering
as
input data the parameters related to the dimensions of the surface of the
double-
sided adhesive tape to be activated and of the support.
Advantageously, the apparatus comprises a control panel by means of which the
process data is entered in the control unit, such as, for example, the
sensitive
dimensions of the double-sided adhesive tape and of the support, as well as
the
adhesive activation temperature, i.e. the process temperature, and the light
absorption coefficients of the two materials, which may be pre-stored so that
the
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operator can enter only the type of material of which the double-sided
adhesive tape
and the support are made, without needing to enter said coefficients each
time.
Other parameters which can be advantageously changed by the operator are, for
example, the position of the double-sided adhesive tape 10 with respect to
support
20, the distance as mentioned of the collimators 31 with respect to the
contact zone,
i.e. with respect to the activation zone of the double-sided adhesive tape,
the
mechanical pressure exerted by said first 40 and second 50 wheel between
double-
sided adhesive tape and support, the power emitted by the laser sources 30,
the
rotation speed of the wheels and thus the feed speed of support and tape.
With regards to the possibility of varying the distance of the collimators 31
from the
contact zone, it is worth noting that with respect to the known type
solutions, and
with respect to the solutions which require a plurality of diodes arranged in
an array
according to the prior patents mentioned above, the solution suggested here
allows
the laser sources 30 to be positioned further away from the heating zone of
the tape,
by using collimated beams, but also if slightly converging or diverging beams
are
used, thus avoiding fumes or the like from fouling the optics. This is
reflected in a
better quality of the end result of the process and lesser maintenance of the
apparatus as compared to the systems of known type.
For this purpose, the apparatus will be provided, as mentioned, with a central
control
unit capable of processing the process data and comparing them with the pre-
stored
data and also with electric and/or pneumatic actuators capable of moving the
wheels
40 and 50 and the collimators 31 of the laser sources 30.
As mentioned, the apparatus will advantageously comprise a metric wheel 60,
commonly known as encoder, which by feeling the surface of support 20 checks
the
actual forward movement of the support itself, and subjects the activation of
the
laser sources 30 to the actual and correct forward movement of the support.
If the metric wheel 60 detects an incorrect movement of support 20, the laser
will be
instantaneously deactivated in order to avoid the risk of fire.
Many changes, modifications, variations and other uses and applications of the
invention will be apparent to those skilled in the art after having considered
the
description and the accompanying drawings which illustrate preferred
embodiments
thereof. Such changes, modifications, variations and other uses and
applications
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which do not differ from the scope of the invention as defined in the appended
claims
and form an integral part of the text are covered by the present invention.
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